PARKLAND, Fla. — Months before authorities say Nikolas Cruz walked into his former high school and slaughtered 17 people, the troubled teen began showing what may have been warning signs he was bent on violence.

“I’m going to be a professional school shooter,” a YouTube user with the screen name “Nikolas Cruz” posted in September.

The 19-year-old had gotten expelled last year from Marjory Stoneman Douglas High School for undisclosed disciplinary reasons. A former Junior ROTC cadet, he bought a military-style AR-15 rifle. And he began to participate in paramilitary drills with a white nationalist organization, according to its leader, Jordan Jereb.

Jereb, head of the Republic of Florida, told The Associated Press on Thursday that his group seeks to create a white state. He said he didn’t know Cruz personally but was told the young man had “trouble with a girl,” and he suggested the timing of the Valentine’s Day attack wasn’t a coincidence.

However, the Leon County Sheriff’s Office in Tallahassee, where the Republic of Florida is based, said it monitors the group’s membership and has seen no ties between the organization and Cruz. Sheriff’s spokesman Lt. Grady Jordan said the Republic of Florida has never had more than 10 members.

Students and neighbors, meanwhile, reported that Cruz threatened and harassed others, talked about killing animals, posed with guns in disturbing photos on social media, and bragged about target practice in his backyard with a pellet gun.

In fact, schoolmates weren’t surprised when Cruz was identified as the gunman in Wednesday’s rampage, said 17-year-old Dakota Mutchler.

“I think everyone had in their minds if anybody was going to do it, it was going to be him,” Mutchler said.

Benjamin Bennight, a Mississippi bail bondsman, was concerned enough after seeing the “professional school shooter” comment on his Youtube channel that he took a screenshot of it on his phone and called the FBI. Two FBI agents visited Bennight the next day.

The FBI said it never spoke to the Florida teen.

“No other information was included in the comment which would indicate a particular time, location or the true identity of the person who posted the comment,” said Brett Carr, a spokesman for the FBI office in Jackson, Mississippi. “The FBI conducted database reviews and other checks but was unable to further identify the person who posted the comment.”

Math teacher Jim Gard told The Miami Herald that before the shooting rampage, Cruz may have been identified as a potential threat. Gard said he believes the school had sent out an email warning teachers that Cruz shouldn’t be allowed on campus with a backpack.

“There were problems with him last year threatening students, and I guess he was asked to leave campus,” Gard told the newspaper.

Student Victoria Olvera, 17, said that Cruz had been abusive to his ex-girlfriend and that his expulsion was over a fight with her new boyfriend. Cruz had been attending another school in Broward County since the expulsion, school officials said.

Jonathan Guimaraes, 17, told the Herald that he had been in JROTC with Cruz. “He was quiet, nice,” Guimaraes said. “That’s how he was able to blend in. He was wearing his JROTC uniform.”